The present invention relates to automatic welding devices, and more particularly to a collet for retaining and positioning T-shaped studs adjacent the surface onto which they are to be welded.
In U.S. Pat. No. 3,582,602 issued to Donald H. Ettinger et al. and assigned to the assignee of the present invention, there is shown an automatic portable gun system for repetitively welding relatively small components in the form of T-studs, or buttons, to panel surfaces. In the above cited patent, there is disclosed a welding gun which has a tubular electrode member with a button-holding means at its projecting ends through which buttons are delivered to the holding means for retention during welding. The tubular member disclosed in that device is a relatively heavy-walled metallic member which is machined to provide a collet at the outer end for holding the stud adjacent the workpiece during the welding operation. The collet, as generally provided in such devices, comprises a metallic member which is machined to provide a plurality of close tolerance fingers at the outer end thereof for gripping the button or stud as it is forced into the end of the tubular member, to be held against the work surface.
While these heavy metallic members prove satisfactory in providing a tubular electrode member and chuck, or collet, combination, there are certain drawbacks to this prior art collet arrangement as described in the aforementioned patent.
First, the manufacture of the collet arrangement requires a plurality of machine operations, some of which are to close tolerances in view of the relatively small size stud or button which is used in the automobile industry, for example.
Also, the welding gun is generally provided with an arc shield which surrounds the button at a fixed distance therefrom, in which case the heavy metallic chuck or collet extends very close to the inner dimension of the arc shield providing little clearance therewith. Over a period of time, the large frontal area of the collet collects a buildup of weld material often called "splatter". When a sufficient quantity of this material collects, there may be arcing between the collet and the workpiece which is detrimental to the welding operation.
It is, therefore, an object of the present invention to provide a collet of the type described which is inexpensive and easy to manufacture in contrast to prior art collets.
Another object of the invention is to provide welding apparatus of the type described wherein the frontal surface of the collet is of less area than prior art devices, and therefore minimizes the probability of arcing due to the collection of spatter material on the collet.